一次春季冰雹天气过程中X波段双偏振雷达的特征分析

Analysis of the Characteristics of X-band Dual-polarization Radar during a Hail Weather in Spring

利用探空资料和咸阳旬邑X波段双偏振多普勒天气雷达对2017年4月26日的冰雹天气过程进行了天气形势分析与双偏振雷达产品的特征分析,结果表明,该次冰雹天气发生在200 hPa西风急流、500 hPa槽后冷平流、高温高湿的中低空条件及地面干冷空气的天气背景下,大气层结具有强不稳定度,垂直方向上存在较强的垂直风切变,均有利于对流运动的发展;西安探空的0℃层高度以及-20℃层高度均十分有利于冰雹在雷暴单体中的维持和增长;边界层附近有逆温层,有利于不稳定能量储存;近地层有强的干冷空气,抬升了中低层的暖湿空气;X波段雷达的反射率因子以及径向速度均表现出典型的雷暴单体回波特征,出现了明显的三体散射回波;存在与强入流和强上升运动对应的弱回波区和悬垂结构,具有明显的回波墙;0℃层高度(3 km)以上有≥50 dBz的强回波;径向速度剖面图上中低层辐合、高层辐散,满足冰雹发生的回波速度特征;X波段双偏振雷达的差分反射率因子(ZDR)、差分传播相移(KDP)、零滞后相关系数(RHV)等参量能有效地提高对冰雹的识别能力。冰雹回波的ZDR、KDP、RHV的取值范围与强降水回波有明显区别,能够有效地区分冰雹回波与强降水回波。在降雹时,2.4°仰角ZDR出现大面积0值、KDP为-1.2~0.45°/km,RHV为0.74~0.95,HCL可以直观地对降水粒子的种类进行判断。X波段双偏振多普勒天气雷达能够较好地反映对流单体的回波特征,双偏振参量能提供更多的冰雹识别特征。

Using sounding data and Xianyang Xunyi X-band double polarization doppler weather radar,the weather situation of a hail process on 26 April 2017 and the characteristics of the dual polarization radar product were analyzed,the results showed that the hail weather occurred in 200 hPa westerly jet,after the 500 hPa trough cold advection,low in the condition of high temperature and high humidity and ground dry cold weather background,atmosphere and had strong stability,vertically exist strong vertical wind shear,is conducive to the development of convective motion;The height of 0℃layer and-20℃layer in Xi’an sounding were favorable for the maintenance and growth of hail in thunderstorm monomer.There was an inversion layer near the boundary layer,which was conducive to the storage of unstable energy.There was strong dry cold air in the near stratum,which lifts the warm moist air in the middle and lower strata.The reflectivity factor and radial velocity of x-band radar showed typical characteristics of thunderstorm monomer echo,and there was obvious three-body scattering echo.There were weak echo regions and overhang structures corresponding to strong inflow and strong rising motion,and there were obvious echo walls.Strong echoes≥50 dBz were observed above the height of 0℃layer(3 km).The radial velocity profile showed convergence in the upper middle and lower layer and divergence in the upper layer,satisfying the echo velocity characteristics of hail.ZDR,KDP,RHV and other parameters of X-band dual-polarization radar could effectively improve the recognition ability of hail.The value range of ZDR,KDP and RHV of hail echo was obviously different from that of heavy precipitation echo,which could effectively distinguish hail echo from heavy precipitation echo.When hail fell,a large area of 0 value and KDP value of 2.4 elevation Angle ZDR appeared from-1.2-0.45°/km,RHV from 0.74-0.95,and HCL could directly judge the types of precipitation particles.The x-band dual-polarization doppler weather radar could better reflect the echo characteristics of convective monomers,and the dual-polarization parameters could provide more hail recognition features.